here we're gonna focus on different creatures in this case and i highly recommend you use these for legacies since they already have been exploring different creatures

- kitsune

this one is actually so interesting, i mean there are nine different types of kitsunes (and not just female, kitsunes can be any gender or non gender)
the first thing i'd focus on when making a kitsune OC is making them Japanese (or at least have one Japanese parent) since kitsune's come from Japan. If you're making them with a white OC it's white washing. Kitsune's have been featured on Teen Wolf, but that's just one version, you can take inspiration or ideas from that, if you want. Let me explain, kitsunes are known for being trickster fox spirits, now they dont all necessarily have to be tricksters if you don't want them to be but it's there if you wanna use it. Something they're also known for is having nine tails. (this seems like a lot right?) Well, Teen Wolf did it in a more symbolic way. Kitsune's have nine of these specific weapons or tools or really anything they connect with in moments of stress or important times, they take it with them and construct into into a symbolized tail. They start off with one and build the collection. I'm also assuming, the more the tails, the more powerful the kitsune. You can also break your tails and use that power for something important like a sacrifice or offering or power boost for others (though I'm not sure if you can get it back).
Kitsune's also function better in backwards (they read books in backwards). It's supposed to be a thing with them, like the fact they can't read forward is a way to suss out if there's a kitsune in the room, since they're known as tricksters, people didnt really like them.
(that's honestly something i remembered from the Teen Wolf show, i didnt look it up, but if that interests you, i hope it turns out to be true).
Also they can live up to like 900+ something years, so great chance to trick your audience into thinking they're vampires. (also, they do have super healing, no special diet, and can have kids, though I'm not exactly sure how the aging goes or how they can die. im kinda sure they're like werewolves, they heal but they can die if its a big wound and such, also if your going in terms of Teen Wolf, im pretty sure if the kitsune has a child, their power sort of transfers to the child and they start to age normally, thats what i got at least)

- mermaids

yeah, i said it, mermaids
now that legacies has been bringing in dozens of different creatures (not something i exactly approve of) i'm justing waiting for a mermaid to drop in. this is where you can take all your knowledge of H2O: Just Add Water to good use, or even explore different versions like the Pirates of the Caribbean ones, or the similar but slightly different Mako Mermaids ones. Though my only advice would be to make it a short story, since having mermaids in Virginia is kinda difficult, Mystic Falls is supposed to be in the middle sorta and getting to the beach would be hours away, so it's not that fun, and a lake isn't the same as the ocean.
so i'd bring in the mermaid(s) and do something small in a legacies fic but then have her(them) leave because they want to be by the water

- banshee's
(bear with me)

i'd do something different, instead of flat out having a banshee, make them have a similar intro like Wade, the guy who turned out to be a fairy. Make a banshee a new student, classified as a witch, but other than finding dead people and every now and then screaming, she can't practice magic. Hell, make her friends with Wade even, or have him be the one to guess that they misclassified her as well. Then after that it's up to you, you can make her(or them) be in denial, they don't want the title of banshee, or they're happy to finally know what they are, or they're freaking out cuz no one else knows what the hell actual banshee's are like and she just started to accept herself as a low-rate witch but now she's a friggin banshee?!
anyway, the only rule for this one is no holland roden and no lydia martin trope, okay? make up a whole new ass OC and then give them the banshee shit, and pick a unique face claim okay? we get enough white strawberry blonde banshee's around here
(but yeah i used these gifs because honestly, when it comes to the Teen Wolf banshee creature, it was really well done, and you can use the actual creature without resorting to holland roden's fc or the lydia trope)

- valkyrie

i read this online and thought 'okay, thats actually not bad'. i think it'd be pretty cool, the exact description for a valkyrie is a female warrior that lives and dies in battle. now you could go either an adult valkyrie like Tessa Thompson from Thor: Ragnorak or for a younger valkyrie you've got different options:

- one thats young but experienced, maybe even the best of her group

- one thats actually really experienced and is actually immortal instead of a growing living person

- one that never got to fight in her group and is maybe even guilty that she never got to fight alongside her sisters; hell maybe she didnt even get to the title of valkyrie and was like one ceremony away from the official title
honestly, you could really explore different methods of using a female warrior

- wendigo

Wendigos are basically cannibals. this was explored for like one episode of Teen Wolf, and it was a whole ass family of wendigo's, they even had a cat. So, the way they worked was they kept semi-living humans in a storage. They had to eat human flesh at least once a day to maintain a healthy diet, other food wasn't wanted by them, and if they don't eat, they will attack and eat the first person they happen upon. Other than that, i know they don't have heightened healing. (or maybe they heal once they've eaten someone). I'm also pretty sure they don't eat dead humans, so it can be a complicated thing to work in the story. Include some morally gray stuff.

- hybrid

oh lords, do you know how awesome it would be to explore a werewolf character made into a hybrid by hope?! okay i legit wrote down everything you need to know and different versions of how it should work in the chapter 'roasting legacies for its untapped potential' its around the early middle i think, but it's all there and how such an interesting premise it is.

but one advice i may give to you:
PLEASE STOP MAKING HYBRIDS

IT STOPPED BEING ORIGINAL SINCE KLAUS AND THEN WITH HOPE

YOU DONT CARE? YOU WANNA MAKE A MERMAID/ANGEL/WITCH/VALKYRIE HYBRID?? FINE GO DO IT IM NOT THE WRITERS POLICE

but i do want to tell you, that you need to let your characters breathe

if you're gonna do a hybrid, stick the established ones in the show, werewolf/vampire or witch/vampire because those are actually plausible and easier to stomach

BUT WHO THE FUCK CARES RIGHT LETS ALL JUST RIGHT JON SNOW AND DAENERYS' CHILD THAT GREW UP ADOPTED BY TONY STARK AND HAVE HER FIND OUT SHE'S A WITCH WHO CAN SHAPESHIFT BC WHY THE FUCK NOT

honestly, doesnt anyone figure that if you keep your character to one thing you can actually write something fun and meaningful? the constant adding of powers and doodads feels like the equivalent of adding bracelets and belts and hats and ties and necklaces and more and more accessories until you can't even the person wearing it. the audience cant see them, we cant connect with them because we're too busy focused on the amount of stuff they got on. at least let your audience know there's someone in there.